"Dirt Map" with procedural shaders?

Can it be done? Any samples advice? Not talking about AO or “self shadows”, but a grunge dirt look.


For overall dirtyness you can set a procedural image to be a stencil texture for procedural dirt textures. As for dirtying concave edges more i’m not sure if that can be done right now without baking AO. It may or may not be possible with nodes though.